We have added Core E, to support a new joint Aim of the POI, described in both in the plans for the coming year in Project 3 and more briefly in Project 1. Dr. Kelsoe, the Pi of this Core, has been working closely with Haynes, Liao, and Harrison, and he is a coauthor (with Haynes, Harrison, and Kepler) ofthe review that describes (and names) B-cell lineage based immunogen design (Haynes, B.F., Kelsoe, G., Harrison, S.C, Kepler, T.B. B-cell-lineage immunogen design in vaccine development with HlV-1 as a case study. Nature Biotechnology 10: 423 (2012), PMC3512202). The novel, single-cell, B-cell culture system will allow us to test this notion on a feasible timescale in a tractable mouse model, and it will yield data that should facilitate more realistic models of the germinal center reaction and antibody affinity maturation (in humans as well as in mice) in the context of an influenza virus immunogen.